The Spurs have played three games in four days, losing all three, including last night's 96-86 defeat to Chicago.
The coach told reporters: "I don't care, that's just an excuse. Everybody tried as hard as they could. I don't know how to measure fatigue. Just go play. We try to watch people's minutes and that kind of thing.
"It doesn't matter who's hurt, or what your schedule is, or anything like that. You go play. Nobody cares. All that matters is the win or the loss. We lost or defensive consistency and they went up."
San Antonio play again on Saturday, hosting the Sacramento Kings.